tylen/ESP-Ventilation
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

16 bit CRC error checking for modbus

Browse Source
This commit is contained in:
jaakkoiot 2022-10-15 15:21:28 +03:00
parent a0635c90b0
commit 2c44373709
1 changed files with 88 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

88
Modbus/inc/crc16.h Normal file
View File

@ -0,0 +1,88 @@
/**
@file
CRC Computations
@defgroup util_crc16 "util/crc16.h": CRC Computations
@code#include "util/crc16.h"@endcode
This header file provides functions for calculating
cyclic redundancy checks (CRC) using common polynomials.
Modified by Doc Walker to be processor-independent (removed inline
assembler to allow it to compile on SAM3X8E processors).
@par References:
Jack Crenshaw's "Implementing CRCs" article in the January 1992 issue of @e
Embedded @e Systems @e Programming. This may be difficult to find, but it
explains CRC's in very clear and concise terms. Well worth the effort to
obtain a copy.
*/
/* Copyright (c) 2002, 2003, 2004 Marek Michalkiewicz
Copyright (c) 2005, 2007 Joerg Wunsch
Copyright (c) 2013 Dave Hylands
Copyright (c) 2013 Frederic Nadeau
Copyright (c) 2015 Doc Walker
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
* Neither the name of the copyright holders nor the names of
contributors may be used to endorse or promote products derived
from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE. */
#ifndef _UTIL_CRC16_H_
#define _UTIL_CRC16_H_
#include <chip.h>
/** @ingroup util_crc16
Processor-independent CRC-16 calculation.
Polynomial: x^16 + x^15 + x^2 + 1 (0xA001)<br>
Initial value: 0xFFFF
This CRC is normally used in disk-drive controllers.
@param uint16_t crc (0x0000..0xFFFF)
@param uint8_t a (0x00..0xFF)
@return calculated CRC (0x0000..0xFFFF)
*/
static uint16_t crc16_update(uint16_t crc, uint8_t a)
{
int i;
crc ^= a;
for (i = 0; i < 8; ++i)
{
if (crc & 1)
crc = (crc >> 1) ^ 0xA001;
else
crc = (crc >> 1);
}
return crc;
}
#endif /* _UTIL_CRC16_H_ */